web2.0 is a like a social community on the internet. youtube, myspace, sqidoo, friendster, facebook, technorati, del.icio.us, digg, netscape, stumbleupon are all web2.0 services. Tha aim of web2.0 to facilitate collaboration and sharing between users. many of these web2.0 usually have pretty high google pagerank. now, these web2.0 comes is so easy for us to create backlinks to our website. you simply sign up for an account, usually there is a chance you can insert your website or blog URL in your profile. there you go, other user will see your website information and they will come to your site, free traffic, isn’t it? also, there is one free one way backlink to your site. the method i am disclosing to you is to help you buildin authority sites for long term use. you can use this method to build direct backlinks to your site on some of the web2.O service. on top of that, I will encourage you to start building your own collection of high pagerank authority nodes on those web2.0 sites. there are usually profile page and favorite page on web2.0 site. you should start to build up backlinks to these profile pages or favorite page on web2.0 service. I called them high authority node. it is easy to obtain backlinks to these profile page or favorite page because you can simply do a comment and you will have a backlink to your profile page. so, the simple trick, participate in the web2.0 community and you can easily build up to of backlinks. once the profile page or favorite page build up authority or command pagerank in the next google update. you can start to create direct backlinks from these high pagerank nodes to your own site. using this method, you will have a handful of these free high authority sites you own.
I find that if you focus on making your accounts great, then you will receive better traffic from these web 2.0 sites. I focus on digg and stumbleupon, and have been doing great.
you are right with focussing in digg and stumbleupon. for suggestion maybe you can adding with squiddo and hubpage
Register your account at various dofollow forums, and social book marking websites. Here is the good list for dofollow forums. and dofollow social book markeing sites.
Most forums are dofollow. Probably easier to have a list of the forums that are nofollow, it would be much shorter. That blog post, however, was a little hypocritical in my opinion. The author says that he/she supports the dofollow movement ... yet his blog is nofollow.
Web2.0 based on community. the key to make our community be loyal and visiting regularly. so we must have quality content and interesting topics.